When two signals are on different frequencies, they can be separated by simple filtering methods. But when the two signals are on the same frequency, they will combine into one (composite) signal having the same frequency. Filtering out one signal will inadvertently filter out the other signal. So separating the two signals using filters is not a viable option. The only known solution is to add to the composite signal a negative of the signal that is desired to be removed. In essence, this is called cancellation via subtraction. U.S. Pat. Nos. 3,696,429; 4,093,923; 4,135,159; 5,966,684; and 4,870,424 describe classic approaches to filtering “unwanted” signals. However, these examples are only effective when the amplitude and particularly the phase (timing) of the interferer is known. In some situations, these requirements cannot be met.
Accordingly, there has been a long-standing need for new systems and methods for co-site, in-band signal extraction and/or recovery, as further described in detail below.